Evaluation of the strength of a new type of detachable joint in a compound glass shell

1. Compound shells with a detachable joint directly connecting the glass elements showed a satisfactory breaking strength under the effect of a single external hydrostatic pressure and can be recommended for working under such conditions up to loads amounting to no more than 0.3 of the calculated value characteristic for monolithic shells similar to them. 2. For the successful realization of direct joining of the glass elements and for eliminating their premature damage and destruction in the joint zone, it is necessary to polish their contact surface with respect to the third class of precision and to provide an arithmetic mean deviation of the profile of the contact surfaces of not more than 0.32 μm. 3. The strength of the assembled shells with a detachable butt joint is determined by the value of the contact strength of the material under conditions of the interaction of glass with glass in the joint in the presence of large specific compressive forces and technological imperfections of the contact surfaces of the joint. The most dangerous type of such imperfections is the presence of chips and gas bubbles on the contact surfaces. Misalignment of the contact surfaces in the plane of the joint, causing the occurrence of inside overhanging edges, also substantially reduces the strength of the compound shells. 4. The direct contact between glass elements on the surface of detachment does not provide a high level of operational capability of the joint in the case of repeated static loading by an external pressure and can be recommended only for one-time (1–10 cycles) use. 5. The cyclic strength of the detachable butt joint of compound shells is entirely determined by the aforementioned factors and its level of stress under conditions of frictional interaction of the contact surfaces. 6. Strengthening of the contact surfaces of glass elements by chemical etching does not improve the joint; the bearing capacity of the compound spherical shell remains at the former level.